This is not the first time that Facebook tried to buy Snapchat. Zuckerberg previously offered $1 billion for Snapchat and was rejected.

In case you don't know what Snapchat is/how it works, here's the quick explanation: You send a photo to a friend, and the photo gets erased after 10 seconds or less from your friend's phone once your friend opens it. You can also draw/write on the photo.

It seems goofy, but it makes a lot of sense. The best way to think about it is this: You can say something to a friend, when you really don't have anything to say.

Part of the reason it's gaining in popularity is that people are worried about leaving a digital trail. A bad tweet, or a dumb Facebook photo can kill your career, or embarrass you. With Snapchat, there is no record, so it's a bit safer.

Snapchat is only two years old, and it has no revenue. However, it's said to have mind-melting engagement numbers with its users.

This is an incredibly bold bet from Zuckerberg. It would be the biggest acquisition in Facebook history. It would be 3X bigger than what it paid for Instagram.

The reason Facebook wanted Instagram and wants Snapchat is that they're mobile photo applications. Facebook owned photos on the desktop, it doesn't own them on mobile.